Soil Organic Carbon Dynamics in Semi-Arid Irrigated Cropping Systems

Abstract

Insufficient characterization of soil organic carbon (SOC) dynamics in semi-arid climates contributes uncertainty to SOC sequestration estimates. This study estimated changes in SOC (0–30 cm depth) due to variations in manure management, tillage regime, winter cover crop, and crop rotation in southern Idaho (USA). Empirical data were used to drive the Denitrification Decomposition (DNDC) model in a “default” and calibrated capacity and forecast SOC levels until 2050. Empirical data indicates: (i) no effect (p = 0.51) of winter triticale on SOC after 3 years; (ii) SOC accumulation (0.6 ± 0.5 Mg ha–1 year–1) under a rotation of corn-barley-alfalfax3 and no change (p = 0.905) in a rotation of wheat-potato-barley-sugarbeet; (iii) manure applied annually at rate 1X is not significantly different (p = 0.75) from biennial application at rate 2X; and (iv) no significant effect of manure application timing (p = 0.41, fall vs. spring). The DNDC model simulated empirical SOC and biomass C measurements adequately in a default capacity, yet specific issues were encountered. By 2050, model forecasting suggested: (i) triticale cover resulted in SOC accrual (0.05–0.27 Mg ha–1 year–1); (ii) when manure is applied, conventional tillage regimes are favored; and (iii) manure applied treatments accrue SOC suggesting a quadratic relationship (all R2 > 0.85 and all p < 0.0001), yet saturation behavior was not realized when extending the simulation to 2100. It is possible that under very large C inputs that C sequestration is favored by DNDC which may influence “NetZero” C initiatives.

Soil health indicators reveal that past dairy manure applications create a legacy effect

“…Other studies conducted in semiarid climates have shown that soils receiving cattle manure can increase SOC (Chatterjee et al., 2017; Deng et al., 2006; Meek et al., 1982; Sommerfeldt et al., 1988). SOC is considered the leading baseline soil health indicator (Lehman et al., 2015) and manure addition is one of the few ways that SOC can be rapidly increased and potentially sustained in semiarid soils (Bierer, Leytem, Dungan, et al., 2021; Dungan et al., 2021; Ghimire et al., 2017) when compared to other management practices such as cover crop and no‐tillage (Acosta‐Martinez et al., 2011; Blanco‐Canqui et al., 2013; Liebig et al., 2019). However, identifying best management practices to maximize C sequestration and maintain crop yields is difficult in semiarid agricultural soils, with a particular lack of knowledge of relationships between SOC stabilization mechanisms and different management practices (Garcia‐Franco et al., 2018).…”

Fertilization strategy affects crop nutrient concentration and removal in semi‐arid U.S. Northwest

“…It is possible that residual N following the alfalfa portion of the present study's rotation supplemented the following year (2018) of corn silage production as contrasts indicated no difference between the control and all other treatments ( P = .519, Table 4). Still, growing season N mineralization in the region can be as high as 100 kg N ha −1 yr −1 , even where no organic amendment is used (Bierer et al., 2021; Koehn et al., 2021) and may be attributable to the lack of corn silage yield response in both 2013 and 2018. Both spring manure and fall manure fertilization strategies inadvertently depressed barley yield in 2014 after significant lodging of these treatments reduced harvestable grain.…”

Cover Crops for Resilience of a Limited-Irrigation Winter Wheat–Sorghum–Fallow Rotation: Soil Carbon, Nitrogen, and Sorghum Yield Responses

“…It is often difficult to observe a significant increase in total SOC and N in a short period in arid and semi-arid environments where biomass input and microbial activity are constrained by low water availability [21]. A denitrification decomposition (DNDC) model simulated a SOC accrual rate of 0.05-0.27 Mg ha −1 yr −1 with grass cover cropping in semi-arid cropping systems [22] However, labile SOC components and soil microbial communities responded within 3-4 years of cover cropping [10,18]. Improved knowledge on cover crop-induced changes in soil organic matter (SOM) fractions, nutrient cycling, and crop yields will help growers sustain crop production with limited irrigation.…”